Most tungsten carbide-cobalt plasma spray powders are produced by mixing fine tungsten carbide with cobalt. These powders are sintered to produce the tungsten carbide-cobalt particles. These materials do not lend themselves to bonding in a low temperature flame spray application.
Good bond strength in cobalt-cobalt contact is desirable in many applications such as hardsurfacing. This would be accomplished by coating tungsten carbide with cobalt. In the application, this would allow the cobalt to melt at lower temperatures than plasma tempertures. Also, these coated powders lend themselves to better bond strength even if used in plasma applications.
An additional advantage of coating is that coarse tungsten carbide can be used. In certain types of wear applications it is desirable to use coarse tungsten carbide particles.